This invention concerns a wireless device that performs transmission of multiple wireless channels arranged within the used frequency band at prescribed frequency intervals.
In a wireless communication system, sometimes a single frequency is used, and sometimes multiple frequencies are used, and in a mobile communication system, in order to make efficient use of the used frequency band, multiple wireless channels are arranged at fixed frequency intervals and wireless devices are used that allow transmission and reception of multiple wireless channels. This invention concerns a wireless device that makes it possible to transmit such multiple wireless channels efficiently.
In a wireless communication system such as a mobile communication system, a high-frequency band of several GHz or more is used to make high-speed wireless transmission possible and increase the number of terminals that can be accommodated within the wireless frequency-band. In order to make efficient use of the wireless frequency band, the frequency spacing is made as narrow as possible, and a composition is used in which the wireless channels are arranged continuously.
The transmission amplifier for amplifying the transmitted signal performs high-efficiency amplification by carrying out the amplification operation near the saturated output. But because of the nonlinearity near the saturated output, the amplified output signal contains a distortion component, which leaks into neighboring channels. Thus, various distortion-compensating amplifiers have been proposed that suppress this distortion component.
FIG. 5 is a diagram for explaining a distortion-compensating amplifier; 51 is a distributor, 52 is a vector adjuster, 53 is a main amplifier, 54 is a delay line, 55 is directional coupler, 56 is a delay line, 57 is a composer, 58 is a vector adjuster, and 59 is an auxiliary amplifier.
The input signal is divided into two by distributor 51; one part is input via vector adjuster 52 to main amplifier 53, whose amplified output signal is input to directional coupler 55, and the other part of the input signal that is divided into two by distributor 51 is input via delay line 54 to directional coupler 55. Delay line 54 is for correcting the delay time between vector adjuster 52 and main amplifier 53.
Accordingly, the amplified output signal from main amplifier 53 and the delayed input signal that goes through delay line 54 go through directional coupler 55 and are combined and output in a prescribed ratio to delay line 56 and vector adjuster 58. The distortion component due to main amplifier 53 consists of the difference between the amplified output signal and the input signal, so this difference is amplified by auxiliary amplifier 59 and is composed and output by composer 57 so as to cancel the distortion component of the amplified output signal of main amplifier 53. In this way it is possible to amplify the input signal while operating main amplifier 53 near its saturation output and to produce an output signal in which the distortion component of the amplified output signal is corrected.
A common amplification system, in which the transmission signals of multiple wireless channels are amplified in common, and an individual amplification system, in which the transmission signal is amplified in correspondence with a wireless channel, are well known. FIG. 6 is a diagram for explaining the common amplification system of a conventional example. In this diagram, 61-1 through 61-n are modulators that correspond to wireless channels, 62 is a composer, 63 is a transmission amplifier, 64 is a transmission-reception signal splitter, 65 is an antenna, and 66 is a receiver.
The modulated output signals of modulators 61-1 through 61-n corresponding to the wireless channels are composed by composer 62 and input to transmission amplifier 63. This transmission amplifier 63 employs, for example, a composition of the aforesaid distortion-compensating amplifiers, amplifies the output signals of the wireless channels in common, and transmits it from antenna 65 via transmission-reception signal splitter 64.
FIG. 7 is a diagram for explaining the individual amplification system of a conventional example; 71-1 through 71-n are modulators that correspond to wireless channels, 72-1 through 72-n are transmission amplifiers corresponding to the wireless channels, 73-1 through 73-n and 74-1 through 74-n are band elimination filters, 75 is a composer, 76 is a transmission-reception signal splitter, 77 is an antenna, and 78 is a receiver.
The transmitted signals corresponding to the wireless channels are modulated by modulators 71-1 through 71-n and are each amplified by its corresponding transmission amplifier 72-1 through 72-n. In this case, the adjacent channel leakage power is eliminated by band elimination filters 73-1 through 73-n and 74-1 through 74-n, they are composed by composer 75, and the composed signal is transmitted from antenna 77 via transmission-reception signal splitter 76.
FIG. 8 is an explanatory diagram of the arrangement of wireless channels; for example, it shows the spectra of wireless channels CH1 through CH4, each of which includes relatively large leakage power into the adjacent channels. Thus a filter having steep attenuation characteristics is proposed. For example, by connecting band elimination filters 91 and 92 having the frequency response shown in FIG. 9, it is possible to have as the transmission signal only the band that is exclusively occupied by a given wireless channel.
As filters for eliminating unwanted waves, superconducting filters are known. For example, by composing a band-pass filter by connecting resonators that are cooled to a superconducting state in multiple cascades, and reducing the resistance to zero, the pass loss of the pass band can be set to zero. In this case, it is known that one can compose a band-pass filter whose unloaded Q is 200,000 and obtain a frequency response of 2 GHz +/xe2x88x925 MHz (for example, see unexamined patent H9-261082 [1997]).
The individual amplification system of the conventional example requires transmission amplifiers 72-1 through 72-n corresponding to the wireless channels, and presents the problem that its wireless device is of a large size. And for each transmission amplifier 72-1 through 72-n, two band elimination filters having characteristics as shown in FIG. 9 are required.
In the common amplification system of the conventional example, the transmission signals corresponding to the wireless channels are amplified in common, and its spectrum is as shown in, for example, FIG. 8. Therefore leakage power into the adjacent channels occurs, and it is nearly impossible to allow only the transmission signal of each wireless channel to pass through with a band-pass filter by a superconducting filter having the aforesaid steep frequency response. That is, it is difficult to narrow the frequency spacing between wireless channels, and with the common amplification system it is no longer possible to make effective use of the wireless frequency band.
Therefore if the wireless channel frequency spacing is broad, it is possible to apply the common amplification system, but if the frequency spacing is made narrow, it is difficult to apply the common amplification system. From such considerations, if the individual amplification system is applied, as mentioned above, this requires transmission amplifiers 72-1 through 72-n and band elimination filters 73-1 through 73-n and 74-1 through 74-n corresponding to the wireless channels, which increases the size and power consumption of the device.
The purpose of this invention is to make it possible to have a smaller-size device with lower power consumption.
The wireless device of this invention performs transmission of multiple wireless channels arranged within the used frequency band at prescribed frequency intervals. A transmission amplifier puts together, in multiple systems, multiple wireless channels with spacing of at least one frequency between them and performs common amplification of the transmission signal of each system. Band elimination filters in cascade connection so as to input the amplified output signal of the transmission amplifier and reduce the adjacent channel leakage power, and a composition means for composing and transmitting the transmission signals output via said band elimination filters.
Additionally, in a wireless device that performs transmission of multiple wireless channels arranged within the used frequency band at prescribed frequency intervals, continuous numbers are assigned to the multiple wireless channels arranged within the used wireless frequency band. The numbered channels are divided into two systems of odd-number wireless channel numbers and even-number wireless channel numbers and coupled to an odd-number wireless channel number transmission unit 1 and an even-number wireless channel number transmission unit 2. A composition means 3 composes the output signals of the odd-number wireless channel number transmission unit 1 and even-number wireless channel number transmission unit 2.
Odd-number wireless channel number transmission unit 1 includes a transmission amplifier 13 that composes the transmission signals of the odd-number wireless channel numbers and performs common amplification. Multiple cascade-connected band elimination filters 14-1 through 14-(k+1) receive as an input the amplified output signal of the transmission amplifier 13 and eliminate the frequency components of the even-number wireless channel numbers of the adjacent channels. Even-number wireless channel number transmission unit 2 includes a transmission amplifier 23 that composes the transmission signals of the even-number wireless channel numbers and performs common amplification. Multiple cascade-connected band elimination filters 24-1 through 24-(j+1) receive as an input the amplified output signal of the transmission amplifier 23 and eliminate the frequency components of the odd-number wireless channel numbers of the adjacent channels.
The composition means includes multiple cascade-connected circulators, one end connected to an end terminal and the other end connected to an antenna and receiver. The composition means can have a composition whereby the transmission signals of the corresponding systems of the transmission amplifiers are respectively input to other multiple circulators except the circulator connected to said antenna and receiver.